I discuss Cohen's guidelines for interpreting the magnitude of correlations, as well as newer, empirically derived guidelines for interpreting correlations.
Gignac, G. E., & Szodorai, E. T. (2016). Effect size guidelines for individual differences researchers. Personality and individual Differences, 102, 74-78.
Cohen, J. (1992). A power primer. Psychological Bulletin, 112(1), 155-159.